This invention relates to electro-mechanical transducers and more particularly to a tubular transducer structure employing a tubular diaphragm member.
The prior art is replete with a number of transducer structures which are primarily employed in the field of medical electronics. These transducer structures are utilized to measure various pressures of the human body to monitor various body functions. Essentially, a widely used type of device employs a housing having an inlet and outlet port. The ports communicate with each other via a cylindrical glass tube which has an aperture at the center. Bonded to the tube so as to close the aperture, is a silicon pressure transducer normally employing piezoresistive devices. In this manner, the pressure to be monitored is applied to the input port while the output port is coupled back to the body of a patient or to a reservoir. Essentially, a saline solution is caused to flow through the tube whereby the pressure exerted on the silicon diaphragm is the pressure of interest. Such devices experience considerable problems in regard to their particular use.
First, as one can ascertain, the silicon diaphragm is relatively expensive and based on the structure, the diaphragm is not isolated from the saline solution. In this manner, a protective coating must be emplaced over the diaphragm 20 so that the solution will not be deleterious to the silicon. In order to protect the device, a gel is coated over the diaphragm. These gels are very difficult to apply and are further very difficult to sterilize. Sterilization is a necessity as the transducer structure has to be sterilized before being used to monitor a body function. The gel must be extremely inert so as not to produce any adverse reactions to the patient, and therefore it has to be relatively pure.
In addition to aforesaid protective coating or alternately isolating electronics is sometimes employed to provide or enhance the required electrical isolation. Such electronics serves to electrically isolate the patient from electrical biasing circuits by the use of appropriate circuitry. Such electronics are expensive and are cumbersome to use with existing patient monitoring apparatus and are considered undesirable from a user standpoint.
Apart from the above considerations, the transducers which are presently employed such as those indicated above must be electrically isolated from the body of the patient. In this manner any electrical impulses to which the patient's body may be subjected to may undesirably couple to the transducer and destroy the same. This problem is associated with the further problem that the transducer must further be isolated from the patient's body as it would be undesirable to subject the patient to any biasing source necessary for transducer operation.
As indicated above, such transducers are therefore associated with a great many problems which have not been adequately solved to the extent that present medical transducers are extremely expensive and difficult to manufacture and maintain.
It is therefore an objective of the present invention to provide a transducer which exhibits reliable operation and which offers isolation and essentially operates to circumvent many of the above described problems.